1. Field of the Invention
This invention relates to a measuring apparatus for measuring various kinds of products irregular in weight such as vegetables and fruits, confectionery, secondary processed goods, perishable foods and the like with constant qualities, and more particularly to an improvement of a measuring apparatus comprising distributing plates for transferring and distributing the product to be measured, a plurality of measuring hoppers arranged about a circumference of the distributing plates for receiving therein the product on the plates at a proper time, measuring means for measuring the transferred product in the hoppers, and computer means for selecting a plurality of measuring hoppers whose weight of product accommodated therein is equal or near to a set weight so as to exhaust the measured product from the hoppers, and more particularly an improvement of a span adjusting mechanism provided at each of the plurality of the measuring hoppers, a span adjusting method and a zero point correcting method of the measuring means.
2. Description of the Prior Art
One example of such a measuring apparatus will be explained with reference to FIGS. 1-3 illustrating the measuring apparatus disclosed in an application Ser. No. 518,632 previously filed by the applicant of this application.
The apparatus shown in the drawings comprises a distributing table 100, carrying-in troughs b.sub.1 -b.sub.10 arranged on both sides of the distributing table 100, pool hoppers c.sub.1 -c.sub.10, measuring hoppers d.sub.1 -d.sub.10 and collecting hoppers 101, whereby product to be measured is transferred on the distributing table 100 in directions shown by arrows and then carried through the carrying-in troughs b.sub.1 -b.sub.10 into the pool hoppers c.sub.1 -c.sub.10 whose bottom plates are opened to transfer the product therein into the measuring hoppers d.sub.1 -d.sub.10. Each of the measuring hoppers d.sub.1 -d.sub.10 is engaged with one end of each measuring means (load cell in this case) which measures a weight of the product in the measuring hopper d.sub.1 -d.sub.10 individually. An output of the measured value from the measuring means is input through an amplifier circuit 102 and an A/D converter 103 into a central processing unit (CPU) which selects a combination of the measuring hoppers whose weight of product is equal or near to a set weight. The product of the selected measured value is transferred into the collecting hopper 101 by opening the bottom plates of the measuring hoppers.
Each of the measuring means e.sub.1 -e.sub.10 is provided with a saucer 104, above which is arranged a reference weight 106 on one end of a rockable rod 105 pivoted at its center to a fixed point. The rockable rod 105 is further provided at the other end with a solenoid 107. When the solenoid is actuated, the reference weight 106 is lowered onto the saucer 104, so that the measuring means e.sub.1 -e.sub.10 is subjected to a load of the reference weight 106 to effect span adjusting. In this manner, a span adjusting mechanism is constructed in the measuring apparatus.
The term "span" used herein is intended to designate a ratio of a weight of product to be measured to an output of the measuring means. If the span is out of a suitable range, precise measurement cannot be effected. It is therefore required to adjust the span for the measuring apparatus of this kind.
In the above measuring apparatus, span adjusting mechanisms are provided for every measuring means e.sub.1 -e.sub.10, which make components of the apparatus complicated and require the same number of solenoids as that of the measuring means to make the apparatus expensive.
Moreover, it is required for the above amplifier circuit 102 to provide a zero point adjusting volume 108 and a span adjusting volume 109.
The above central processing unit (CPU) stores previously memorized output data from the measuring means e.sub.1 -e.sub.10 under no-load condition (initial load) and subtracts the output data under no-load condition from output data under loaded condition when the product to be measured has been transferred in the measuring hoppers to calculate the weight of the product. Accordingly, the output data under no-load condition is required to be exact. If a zero point of the measuring means is changed due to creep of components in such means, change in temperature or the like it is necessary to correct the zero point. It is often required to correct the zero point during operation of the apparatus.
In general, it is required to remove the product from the measuring hoppers to bring the measuring means into a no-load condition. However, such a removal of the product every time of zero point correction is troublesome. In the above measuring apparatus having a number of measuring means whose measured values are to be selected, particularly, the removal of the product every time of zero point correction is not only troublesome but also lowers the operating efficiency for selecting and combining the measured values. Moreover, the one or more measuring hoppers whose measuring means are subjected to the zero point correction cannot take part in the combination of the selected measured values, thereby reducing the total number of the combination so as to lower the accuracy of the combination.
With the above measuring apparatus, moreover, the span adjusting has been effected in the following manner.
(1) The bottom plates of the measuring hoppers d.sub.1 -d.sub.10 associated with the measuring means e.sub.1 -e.sub.10 whose spans are to be adjusted are opened to evacuate the relevant measuring hoppers.
(2) The zero point adjusting volume 108 is operated to adjust the zero point of each circuit of the measuring means.
(3) The solenoid 107 for each of the measuring means to be adjusted is switched on to load or put the reference weight 106 onto the saucer 104.
(4) The span adjusting volume circuit 109 is operated to adjust the span of each of the measuring means.
(5) The solenoid 107 is turned off to remove the reference weight 106 from each saucer 104.
In the adjusting method, however, the volumes are manually adjusted so that the adjusting operation is inconvenient and requires much time which lowers the rate of operation of the measuring apparatus. Furthermore, it is objectionably necessary to return onto the distributing table the product exhausted when the bottom plates of the measuring hoppers were opened.